We propose here the development of an optical waveguide-based spectroscopic instrumentation in the ultra-violet (UV) region for research of unprecedented sensitivity in biomolecular thin-film assemblies. Single-mode, integrated optical waveguides (IOW) have shown to provide the ultimate sensitivity to perform attenuated total reflection (ATR) absorption spectroscopy of molecular films and has been successfully demonstrated in protein films at the visible spectral region. However, the lack of adequate optical waveguide materials has limited the extension of the technique into the UV region, which represents a serious limitation as most important spectroscopic fingerprints of biomolecular species are located in the deep UV (300 -190 nm) region, e.g. the aromatic groups of the protein amino acids tryptophan, tyrosine, and phenylalanine. The successful development of UV-compatible optical waveguides will allow us to implement a highly sensitive, single-mode IOW ATR spectrometer at the UV spectral region (450 -190nm). In this project we will focus on the critical and enabling developments of i) optical materials and process that can produce single-mode lOWs with low propagation loss in the UV spectral range, and ii) a novel architecture for the single-mode, IOW-ATR spectrometer that will greatly simplify its use for the investigation of molecular assemblies at the solid-liquid and solid-gas interfaces. To validate the capabilities of the novel technology, we will apply it to several case studies including specific investigations of protein behavior at interfaces. Immobilization and adsorption of proteins and other biomolecules to solid surfaces is critical in the development of solid-phase-based bioanalytical techniques, biocompatible materials, and biosensors. Gaining a more detailed and accurate understanding of how proteins adsorb, in what amount and conformation, and establishing a systematic correlation between the physical/chemical environment and their bioactivity is an essential knowledge for designing novel biointerfacial processes and biomaterials for implants, and for creating new biomedical diagnostics and drug delivery systems.